Enhancing ¹O₂ Generation Performance by Regulating C and N Coordination for Efficient Fenton-Like Catalytic Process

Singlet oxygen (¹O₂), a vital reactive species, exhibits excellent organic pollutant degradation selectivity in Fenton-like reactions. Recognizing and controlling the structure-activity relationship of single-atom catalysts (SACs) is essential to achieving the highly efficient and selective generation of ¹O₂ for various practical applications. Here, three iron single-atom catalysts with different coordination configurations (Fe_SAC─N₄, Fe_SAC─N₃-C_1, and Fe_SAC─N₂─C₂) are prepared to modulate the selective generation of ¹O₂ by activating peroxymonosulfate (PMS). Replacing N coordinated to Fe atoms with C increases ¹O₂ selective generation thus enhancing the Fenton-like reaction activity. Specifically, Fe_SAC─N₂─C₂ presents the optimal catalytic activity, high stability, and environmental tolerance. Moreover, the ¹O₂ selectivity increases as the N coordination number decreases, which is in the order of Fe_SAC─N₄ (73%) < Fe_SAC─N₃─C₁ (82%) < Fe_SAC─N₂─C₂ (90%). DFT calculations demonstrate that replacing N with C enhances the electrophilicity and electron transfer capacity, optimizes the d-band center, facilitates reactant adsorption, and reduces the energy barrier, thus facilitating ¹O₂ production and enhancing the Fenton-like reaction activity. This study reveals the underlying catalytic trends and mechanisms of catalyst structure-activity relationships for high selective generation of ¹O₂ by PMS activation, thus providing guidance for developing catalysts capable of highly selective organic pollutant degradation.